In order to increase the fatigue life of certain structural members, particularly those used in aircraft, it has long been recognized that the cold working of holes, which receive fasteners, is advantageous. Customarily, this is achieved by inserting a mandrel and sleeve into a hole, then pulling the mandrel through the sleeve and hole with a powered actuator such as a hydraulic unit. The mandrel and sleeve combination has an outer diameter that is slightly larger than the initial hole diameter; during this process the hole will be expanded to the full diameter of the mandrel plus the sleeve, and after it is pulled through, the finished hole diameter is greater than the start hole but less than the mandrel/sleeve combination. The end result will be a strengthening of the metal structure in the vicinity of the hole wall due to the mandrel cold working.
In initial fabrication of structural members sufficient clearance is usually available so that a powered mandrel can be employed. However, when repairs or retrofitting are in order, limited access exists and powered actuators are often no longer possible. Accordingly, a need exists for displacing the mandrel through a hole for its cold working but in an area where clearance is limited.